THE SNP have been accused by Labour of "playing juvenile politics" after voting against the proposal to launch airstrikes on the Islamic State (IS) in Iraq.

Angus Robertson, the Nationalists' foreign affairs spokesman, expressed revulsion at the militia group's reign of terror, which includes beheadings, crucifixions and rapes, and agreed international co-operation was required.

However, during an impassioned eight-hour debate, the Moray MP yesterday told the Commons that because there was no coherent plan to "win the peace" in the Coalition's motion then SNP MPs would vote against it.

He said there was "deep scepticism for the potential of mission creep and a green light for a third Iraq war", given what had happened previously in Iraq, Afghanistan and Libya.

He added: "The motion asks for a green light for military action which could last for years [but] there is no commitment in the motion for post-conflict resolution."

Later, Thomas Docherty, shadow deputy Commons leader, said: "We are facing a humanitarian crisis on an unprecedented level in the Middle East and the SNP are playing juvenile politics when hundreds of thousands of Christians and Muslims face genocide and the West, in partnership with the Arab countries, are trying to save lives."

Another Labour MP suggested the Nationalists seemed to be continuing the Yes campaign, "playing party politics rather than making decisions in the best interests of the country".

The RAF, which has six Tornados in Cyprus, could now attack IS after recalled MPs voted 524 to 43, a majority of 481, in favour of airstrikes.

The UK Government motion easily won because of support from Labour, but MP Rushanara Ali, a shadow education minister, abstained and resigned from her frontbench post.

Inverclyde MP Iain McKenzie was sacked as parliamentary aide to Vernon Coaker, the Shadow Defence Secretary, after voting against the motion. Some 23 Labour MPs defied the whip, among them five Scots: Dame Anne Begg, Ian Davidson, Katy Clark, Mark Lazarowicz and Mr McKenzie. Another 14 Scottish Labour MPs did not take part; some, it is believed, were in Cyprus for the wedding of MP Gregg McClymont.

During the debate, David Cameron said the brutal murder of David Haines, who was raised in Perth, and the threat from IS to kill two more British hostages showed the danger was a real and proven one to the people of the UK.

Mr Haines' widow Dragana expressed support for UK military action.

Declaring there was "no walk on by option", the Prime Minister said the UK had "a duty" to act with the alliance of Western and Arab nations but warned destroying IS would take years.

He also held out the prospect of extending UK involvement to airstrikes in Syria, saying he believed such a move was legal but "more complicated".

Mr Cameron reserved the right to act without parliamentary approval if there was an urgent humanitarian crisis that justified it.

During the debate, the PM said he was not prepared to "subcontract" the protection of British streets from terrorism to other countries' air forces. He said: "This is about psychopathic terrorists who are trying to kill us. We do have to realise that, whether we like it or not, they have already declared war on us."

Labour leader Ed Miliband - who a year ago forced the PM to abandon plans for airstrikes in Syria - said there was "unease" about intervention but argued that current circumstances were different, given the request from a democratic government and an international coalition. He told MPs: "We cannot simply stand by against the threat of [IS]."

Respect MP George Galloway argued that airstrikes should be left to regional powers such as Saudi Arabia and Turkey, noting: "The last people who should be returning to the scene of their crimes are the UK, US and France."

The SNP's stance has echoes of Alex Salmond's in 1999, when the SNP leader described Nato bombing in Yugoslavia as "an act of dubious legality" and "unpardonable folly".